Collected sand processing method

ABSTRACT

A method and apparatus are provided to process collected sand. This method and apparatus allow the moisture content to be adjusted and the addition of a binder to be facilitated to renew the collected sand as casting sand for future use. Also, defective castings are prevented when they are made by a main mold using the renewed casting sand. The sand-collecting means can be compact. The method is performed and the apparatus is operated by separating a main mold of green sand, after casting is conducted, into parts unaffected and affected by the molten metal heat, adjusting the moisture content of the part unaffected by molten metal heat for use as facing sand in the next main mold making, and adding a binder and adjusting the moisture content of the part affected by the molten metal heat for use as back sand in making the next main mold.

FIELD OF INVENTION

This invention relates to a method and apparatus for processing sandthat is collected after a main mold made of green sand (or a main mold)is obtained after casting.

BACKGROUND OF INVENTION

Japanese Patent Laid-open Publication No. Hei. 10-249482 discloses aconventional method for processing collected salad wherein the main moldis separated into sand that has been exposed to a high temperature frommolten metal and outer sand surrounding that sand, wherein the sands arecollected, wherein water and a binder are added to the sand that hasbeen exposed to a high temperature, and wherein then the sand is mixedwith the outer sand, the mixture to be reused.

However, the conventional method for processing collected sand includessome disadvantages. For example, it is difficult to adjust the moisturecontent in the collected sand and to add a binder to it when it isreused as molding sand. Also, a defect can be caused in a mold when itis made by the main mold that is made by reusing the molding sand. Also,a large system is needed to separate affected and unaffected sand and tocollect them through respective paths.

This invention has been conceived to overcome these disadvantages. Theobject of this invention is to provide a method and apparatus forprocessing collected sand. This method and apparatus allow the moisturecontent in collected sand to be easily adjusted and a binder to beeasily added to the collected sand so as to renew it as molding sand.Also, no defect is caused in the mold even if it is made by the renewedmolding sand, and the apparatus for collecting sand can be compact.

SUMMARY OF INVENTION

To achieve the objects stated above, a method is provided for processingsand that is collected, after casting, from a main mold of green sand.The method includes the steps for separating the main mold of green sandinto a part that has been unaffected by the heat of molten metal and apart that has been affected by the heat of the molten metal, adjustingthe moisture content in the part that has been unaffected by the heat ofthe molten metal to use that part as facing sand when a new main mold ismade, and adding a binder to the part that has been affected by the heatof the molten metal and adjusting the moisture content in the part touse it as back sand when a new main mold is made.

Also, a method is provided for processing sand that is collected, aftercasting, from a main mold made of green sand. This method includes thesteps of separating each main mold of green sand into a part that hasbeen unaffected by the heat of the molten metal and a part that has beenaffected by the heat of the molten metal, separately collecting the partthat has been unaffected by the heat of the molten metal and the partthat has been affected by the heat of the molten metal adding a binderto the part that has been affected by the heat of the molten metal andadjusting the moisture content in that part, mixing at a predeterminedratio the part to which a binder is added and in which the moisturecontent is adjusted with the part that has been unaffected by the heatof the molten metal, and adjusting the moisture content in the mixedmaterial to use it as molding sand.

Also, a method is provided for processing sand that is collected aftercasting from a main mold made of green sand. This method includes thesteps of separating each main mold of green sand into a part that hasbeen unaffected by the heat of molten metal and a part that has beenaffected by the heat of the molten metal, separately collecting the partthat has been unaffected by heat of molten metal and the part that hasbeen affected by the heat of the molten metal mixing at a predeterminedratio the two kinds of the collected sand, adding a binder to the mixedsand, and adjusting the moisture content in the mixed sand to use it asmolding sand.

Also, a method is provided for processing green sand for a main moldthat is obtained by separating and collecting a main mold of green sandafter casting. This method includes the steps of separating each mainmold of green sand into a part that has been unaffected by the heat ofmolten metal and a part that has been affected by the heat of the moltenmetal, separately storing in respective storing means the part that hasbeen unaffected by the heat of molten metal and the part that has beenaffected by the heat of the molten metal, processing and collecting thesand that has been separated and stored in the respective storing meansby transferring the sand through the same path at different times, andcollecting them in respective storing means, mixing at a predeterminedratio the two kinds of collected sand, and adjusting the moisturecontent in the mixed sand to use it as molding sand.

This processing method includes the step for collecting the parts bytransferring the parts through the same path at different times. Thus,this method allows the moisture content in the parts to be easilyadjusted and allows the binder to easily be added to the parts. Also, nodefect is caused in molds even if they are made by the renewed moldingsand. A large system is unneeded.

Also, an apparatus is provided for processing sand that is separated andcollected from a main mold made of green sand after casting. Thisapparatus comprises means for separating each main mold made of greensand into a part that has been unaffected by the heat of molten metaland a part that has been affected by the heat of the molten metal andstoring the parts, and means for separately collecting the part that hasbeen unaffected by the heat of molten metal and the part that has beenaffected by the heat of the molten metal, which parts are then separatedand stored. This apparatus also comprises means for separately storingthe part that has been unaffected by the heat of the molten metal andthe part that has been affected by that heat, which parts are separatelycollected, clay- and moisture-content-adjusting means for adding abinder to the part that has been affected by the heat and adjusting themoisture content in the part, blending means for blending the part thathas been unaffected by the heat of the molten metal and the part thathas been affected by that heat at a predetermined ratio, and mixingmeans for adjusting the moisture content in the parts and mixing theparts.

This apparatus does not need a plurality of collecting means. Thus, thisapparatus can be compact. Also, this apparatus allows the moisturecontent in the parts to be easily adjusted and allows the binder to beeasily added to the parts. Also, no defect is caused in molds even ifthey are made by the renewed molding sand. A large system is unneeded.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart describing a first embodiment of this invention.

FIG. 2 is a flowchart describing a second embodiment of this invention.

FIG. 3 is a flowchart describing a third embodiment of this invention.

FIG. 4 is a flowchart describing a fourth embodiment of this invention.

DETAILED EXPLANATION OF PREFERRED EMBODIMENT

The step of this invention for separating the main mold after castinginto a part that has been affected by the heat of molten metal and apart that has been unaffected by that heat can be achieved by making thepressure negative in an airtight member.

That is, just after casting the main mold is put in an airtight memberand then the pressure in the airtight member is made negative. Thisresults in the boiling point of all the moisture in the main mold thatcontains the moisture in a water-condensed layer being lowered, so thatthe part that has been unaffected by the heat of the molten metal isbroken and separated from the other part.

The words “just after casting” denote the time when the molten metal inthe main mold is hardened and a mold is defined.

If each main mold of green sand is separated into a part that has beenunaffected by the heat of molten metal and a part that has been affectedby that heat, the parts can be prevented from being mixed. Also, addingtoo much of an additive agent is prevented, so that controlling themoisture content can be relatively easy. If the main molds areindividually separated, then even if defective molds are made, theconditions for the mold types, the molten metal, etc., can be easilydefined, so that this problem can be easily overcome.

Based on FIG. 1 a first embodiment of this invention is now discussed.As in FIG. 1, molten metal is cast in a main mold that is molded by amolding machine. Then, after casting the main mold is put in an airtightmember. The mold material in the main mold has, at an outer part, alayer (or a condensed-water layer) in which much water is collectedwhich layer is heated by the heat of the mold material to a hightemperature. If the pressure in the airtight member is rapidly decreasedto be negative, the boiling point of the water in the main mold thatcontains the water in the condensed-water layer is lowered, and thus thewater is boiled. As a result, the part that has been unaffected by theheat of the molten metal is broken.

Thus, the main mold is separated into the part that has been unaffectedby the heat of the molten metal and the part that has been affected bythat heat (or a primary mold breaking), The part that has beenunaffected by the heat of the molten metal is collected as collectedsand (or primarily separated sand), and then is crushed by a crushingmachine into particles. Then metal pieces are removed from the particlesby a magnetic separator. The particles are sifted by a screen to selectparticles having predetermined sizes. The collected and sifted sand istemporarily held by a sand bin. Then, the sand is taken out from thesand bin. Then the moisture in the sand is adjusted by a mixer. Themixed sand is used as facing sand to mold the main mold.

The part that has been affected by the heat of the molten metal isseparated from the molding material (or a secondary mold breaking) by ablast-processing operation, etc., because this part is attached to themolding material. That separated part, which has been affected by theheat of the molten metal (or secondarily separated sand), is cooled, andthen sifted by a screen to take out particles having predeterminedsizes. Any metal pieces are removed by the magnetic separator from thecollected and sifted sand. The sand is mixed with a binder and water byadding them to the sand bit by bit. The mixed collected sand is used asback sand when the main mold is molded.

The first embodiment is a method for processing sand that is collectedfrom a main mold of green sand after casting. By this method the mainmold is separated, after casting, into a part that has been affected bythe heat of the molten metal and a part that has been unaffected by thatheat. The moisture content contained in the part that has beenunaffected is adjusted. That part is used as facing sand for a followingmolding operation using the main mold. A binder is added to the partthat has been affected by the heat of the molten metal. The moisturecontent in this part is adjusted. This part is used as back sand for thefollowing molding operation of the main mold. Thus, many practicaleffects are produced by this embodiment. That is, this embodiment allowsthe adjustment of the moisture content and the addition of the binder tobe easily made. No defect is made in molds even if they are made fromthe main molds that are made of the renewed molding sand.

Based on FIGS. 2 and 3, second and third embodiments of this inventionare now discussed. As in FIG. 2, in the second embodiment, casting isconducted by using a main mold that is molded by a molding machine.Then, the main mold is put, after casting, in an airtight member. Themold material in the main mold has, at an outer part, a layer (or acondensed-water layer) in which much water is collected, which layer isheated by the heat of the mold material to a high temperature. If thepressure in the airtight member is rapidly decreased, the boiling pointof the water in the main mold that contains the water in thecondensed-water layer is lowered and thus the water is boiled. As aresult, the part that has been affected by the heat of the molten metalis broken.

Thus, the main mold is separated into the part that has been unaffectedby the heat of the molten metal and the part that has been affected bythat heat (or a primary mold breaking). The part of each main mold thathas been unaffected by the heat of the molten metal is broken andseparated, and then is collected as collected sand (or primarilyseparated sand). Then the collected sand is crushed by a crushingmachine into particles. Then, any metal pieces are removed from theparticles by a magnetic separator. The particles are sided by a screento take out particles having predetermined sizes. The collected andsifted sand is temporarily held in a sand bin.

The part that has been affected by the heat of the molten metal isseparated from the molding material (or a secondary mold breaking) by ablast processing operation, etc., because this part is attached to themolding material. That separated part, which has been affected by theheat of the molten metal (or secondarily separated sand), is cooled by asand cooler to a predetermined temperature, and then sifted by a screento take out particles having predetermined sizes. Any metal pieces areremoved by the magnetic separator from the collected and sifted sand.The sand is mixed with a binder and water by adding them to the sand bitby bit. The mixed and collected sand is temporarily stored in the sandbin.

Then, the two kinds of collected sand that are separately stored in twosand bins are taken out from the sand bins at each preset quantity andare put into the mixer. The collected sand is then mixed by the mixerwith water added little-by-little, and is used as molding sand.

This embodiment is a method for processing sand that is collected from amain mold made of green sand after casting. By this method each mainmold is separated, after casting, into a part that has been affected bythe heat of the molten metal and a part that has been unaffected by thatheat. The part that has been affected by the heat of the molten metaland the part that has been unaffected by that heat are collectedseparately. A binder is added to the part that has been affected by theheat of the molten metal. The moisture content in this part is adjusted.This part is mixed with the part that has been unaffected by the heat ata predetermined ratio. Finally, the water content contained in the mixedsand is adjusted. The sand is used as molding sand. Thus, many practicaleffects can be produced by this invention. That is, this embodimentallows the adjustment of the moisture content and the addition of thebinder to be easily made. No defect is made in molds even if they aremade from the main molds that are made of the renewed molding sand.

FIG. 3 shows a third embodiment of this invention. As in FIG. 3, in thisembodiment, casting is conducted using a main mold that is molded by amolding machine. Then, the main mold is put, after casting, in anairtight member. The mold material in the main mold has, at an outerpart, a layer (or a condensed-water layer) in which much water iscollected, which layer is heated by the heat of the mold material to ahigh temperature. If the pressure in the airtight member is rapidlydecreased, the boiling point of the water in the main mold that containsthe water in the condensed-water layer is lowered and thus the water isboiled. As a result the part that has been unaffected by the heat of themolten metal is broken.

Thus, the main mold is separated into the part that has been unaffectedby the heat of the molten metal and the part that has been affected bythat heat (or a primary mold breaking). The part of each main mold thathas been unaffected by the heat of the molten metal is broken andseparated, and then is collected as collected sand (or primarilyseparated sand) Then, the collected sand is crushed by a crushingmachine into particles. Then, any metal pieces are removed from theparticles by a magnetic separator. The particles are sifted by a screento take out particles having predetermined sizes. The collected andsifted sand is temporarily held by a sand bin.

The part that has been affected by the heat of the molten metal isseparated from the molding material (or a secondary mold breaking) by ablast processing operation, etc., because this part is attached to themolding material. That separated part, which has been affected by theheat of the molten metal (or secondarily separated sand), is cooled by asand cooler to a predetermined temperature, and then sifted by a screento take out particles having predetermined sizes. Metal pieces areremoved by a magnetic separator from the collected and sifted sand. Thesand is temporarily stored in the sand bin.

Then, the two kinds of the collected sand that are separately stored intwo sand bias are taken out from the sand bins at each preset quantityand are put into the mixer. The collected sand is then mixed by themixer with a binder and water added little-by-little, and is used asmolding sand.

The third embodiment is a method for processing sand that is collectedfrom a main mold made of green sand after casting. By this method eachmain mold is separated, after casting, into a part that has beenaffected by the heat of the molten metal and a part that has beenunaffected by that heat. The part that has been affected by the heat ofthe molten metal and the part that has been unaffected by that heat arecollected separately. The two kinds of collected sand are mixed at apredetermined ratio. Then, a binder is added to the mixed sand. Also,the moisture content in the mixed sand is adjusted. It is used asmolding sand. Thus, many practical effects are produced by thisinvention. That is, this embodiment allows the easy adjustment of themoisture content and the addition of a binder. No defect is made inmolds even if they are made of the main molds that are made of therenewed molding sand.

Based on FIG. 4 a fourth embodiment of this invention is now discussed.This embodiment relates to an apparatus for processing green sand for amain mold that is obtained by separating the main mold made of greensand after casting, and by collecting them. As in FIG. 4, the apparatushas a separating and storing means. It comprises a separating means forseparating each main mold made of green sand into a part that has beenunaffected by the heat of the molten metal and a part that has beenaffected by that heat (or means performing primary and secondarybreakings), and a storing means for storing the separated parts (or aprimary separating hopper and a secondary separating hopper).

Downstream of the separating and storing means a collecting means islocated. It includes a magnetic separator, a screen, a water-addingapparatus, a sand cooler, and means for connecting them. The collectingmeans separately collects the part that has been unaffected by the heatof the molten metal and the part that has been affected by that heat,which parts have been previously separated and collected.

Downstream of the collecting means two storing means (or two sand bins)are located for collected sand, to separately collect the part that hasbeen unaffected by the heat of the molten metal and the part that hasbeen affected by that heat, which parts are separated and collected.

Downstream of the storing means is located a clay- andmoisture-content-adjusting means to add a binder to the sand and toadjust the moisture content in the sand.

Downstream of the clay- and moisture-content-adjusting means is locateda blending means for blending the collected sand that is adjusted by theclay- and moisture-content-adjusting means and the collected sand thathas been unaffected at a predetermined ratio, and a miring means formixing them after the moisture is adjusted in them.

Now the operation of the fourth embodiment of this invention isdiscussed. As in FIG. 4, by the method for processing the green sand fora main mold, casting is conducted using the main mold that is molded bya molding machine. Then, the main mold is put, after casting, in anairtight member. The mold material in the main mold has, at an outerpart, a layer (or a condensed-water layer) in which much water iscollected, which layer is heated by the heat of the mold material to ahigh temperature. If the pressure in the airtight member is rapidlydecreased, the boiling point of the water in the main mold that containsthe water in the condensed-water layer is lowered, and thus the water isboiled. As a result, the part that has been unaffected by the heat ofthe molten metal is broken.

Thus, the main mold is separated into the part that has been unaffectedby the heat of the molten metal and the part that has been affected bythat heat (or a primary mold breaking). The part of each main mold thathas been unaffected by the heat of the molten metal is broken andseparated, and then is collected as collected sand. Then the collectedsand is crushed by a crushing machine into particles. Then, theparticles are temporarily stored in a primary hopper for separated sand.

The part that has been affected by the heat of the molten metal isseparated from the molding material (or a secondary mold breaking) by ablast-processing operation, etc, because this part is attached to themolding material. That separated part, which has been affected by theheat of the molten metal, is temporarily stored in a secondary hopperfor separated sand (or storing means) differing from the primary hopper.

Then, any metal pieces are removed from the primarily separated sand bya magnetic separator. The primarily separated sand is sited by a screento take out particles having predetermined sizes. When there isinsufficient water in the sand, a moisture-content-adding apparatus addswater to the sand. Then, the sand is cooled by the sand cooler to apreset temperature and temporarily stored in a sand bin (or storingmeans for collected sand).

When a set time has passed after the primarily separated sand has beencollected, a secondarily separated sand is transferred through the samepath to remove metal pieces from the sand and to be sifted to take outparticles having predetermined sizes. When the sand has insufficientwater, more water is added. Then, the secondarily separated sand iscooled by the sand cooler to a preset temperature and temporarily storedin another sand bin (or storing means).

The primary and secondary sands are processed at different tines throughthe same path. The processing operations for them differ. For example,water is added depending on the temperatures and the water content inthe collected sand. Also, the conditions of the magnetic separator andthe screen may be changed. Thus, the sand may be adjusted before it istransferred to the storing means for the collected sand, so thatsubsequent processing operations can be simplified.

The two kinds of collected sand that are separately stored in two sandbins are taken out at each predetermined quantity from the sand bins,and put into the mixer. Then, the sand is mixed with water and a binderby adding them little-by-little. The sand is used as molding sand. Thebinder and water may be preliminarily added to the sand before the sandis taken out of the sand bins and put in the mixer.

In the fourth embodiment, after the primarily separated sand iscollected, the secondarily separated sand is collected. However, theorder may be changed. In that case a timer or a level switch is used tochange the order. The two storing means for separated sand may be builtas one unit if it can separately store the primarily separated sand andthe secondarily separated sand.

As discussed above, the method for the fourth embodiment is a method forprocessing green sand for a main mold that is separated and collectedafter casting is conducted from a main mold of green sand. By thismethod each main mold is separated, after casting, into a part that hasbeen unaffected by the heat of the molten metal and a part that has beenaffected by that heat. The part that has been unaffected by the heat ofthe molten metal and the part that has been affected by that heat arecollected separately in respective storing means for storing theseparated sand. The parts of the sand that are stored in the storingmeans are transferred through the same path at different times. Then,the two kinds of collected sand are mixed at a predetermined ratio, andtheir moisture content is adjusted. The sand is used as molding sand.Thus, this embodiment allows the adjustment of the moisture content andthe addition of the binder to be easily made. No defect is made in moldseven if they are made of the main molds that are made of the renewedmolding sand. A large system is not needed.

Also, the apparatus for the fourth embodiment is an apparatus forprocessing green sand for a main mold that is separated and collectedfrom a main mold of green sand after casting. This apparatus includes aseparating and storing means to separate each main mold, after castingis conducted, into a part that has been unaffected by the heat of themolten metal and a part that has been affected by that heat and to storethem, a means for separately collecting the part that has beenunaffected by the heat of the molten metal and the part that has beenaffected by that heat, and a means for separately storing the part thathas been unaffected by the heat of the molten metal and the part thathas been affected by that heat which parts are separately collected. Theapparatus also includes a clay and moisture-content-adjusting means foradding a binder to the part that has been affected by the heat andadjusting the moisture content in that part, a blending means forblending the part that has been unaffected by the heat of the moltenmetal and the part that has been affected by that heat at apredetermined ratio, and a mixing means for adjusting their moisturecontent and for mixing the parts. Thus, this embodiment allows the easyadjustment of the moisture content and the addition of the binder, so asto use the sand as molding sand. No defect is made in molds even if theyare made of the main molds that are made of the renewed molding sand. Alarge system is not needed.

What is claimed is:
 1. A method for processing collected sand that iscollected from a main mold of green sand after casting is conducted,including the steps of separating the main mold of green sand into apart that has been unaffected by heat of molten metal and a part thathas been affected by the heat of the molten metal, adjusting themoisture content in the part that has been unaffected by the heat of themolten metal to use the part as facing sand when a new main mold ismade, and adding a binder to the part that has been affected by the heatof the molten metal and adjusting the moisture content in the part touse the part as back sand when a new main mold is made.
 2. The method ofclaim 1 wherein the step for separating the main mold of green sand,after casting is conducted, into a part that has been unaffected by heatof molten metal and a part that has been affected by the heat of themolten metal is achieved by making the pressure negative in an airtightmember in which the green sand mold is put just after casting.
 3. Amethod for processing collected sand that is inflected from a main moldof green saint after casting is conducted, including the steps ofseparating each main mold of green sand into a part that has beenunaffected by heat of molten metal and a part that has been affected bythe heat of the molten metal, separately collecting the part that hasbeen unaffected by heat of molten metal and the part that has beenaffected by the heat of the molten metal, adding a binder to the partthat has been affected by the beat of the molten metal and adjusting themoisture content in the part, mixing at a predetermined ratio the partto which a binder is added and in which the moisture content is adjustedwith the part that has been unaffected by the heat of the molten metal,and adjusting the moisture content in the mixed material to use it asmolding sand, wherein the step for separating the main mold of greensand into a part that has been unaffected by heat of molten metal and apart that has been affected by the heat of the molten metal is achievedby making the pressure negative in an airtight member in which the greensand mold is put just after casting.
 4. A method for processingcollected sand that is collected from a main mold of green sand aftercasting is conducted, including the steps of separating each main moldof green sand into a part that has been unaffected by heat of moltenmetal and a part that has been affected by the heat of the molten metal,separately collecting the part that has been unaffected by heat ofmolten metal and the part that has been affected by the heat of themolten metal, mixing at a predetermined ratio the two kinds of collectedsand, and adding a binder to the mixed sand and adjusting the moisturecontent in the mixed sand to use it as molding sand.
 5. The method ofclaim 4 wherein the step for separating the main mold made of green sandinto a part that has been unaffected by heat of molten metal and a partthat has been affected by the heat of the molten metal is achieved bymaking the pressure negative in an airtight member in which the greensand mold is put just after casting.
 6. A method for processing greensand for a main mold that is obtained by separating and collecting amain mold of green sand after casting is conducted, including the stepsof separating each main mold of green sand into a part that has beenunaffected by heat of molten metal and a part that has been affected bythe heat of the molten metal, separately staring in respective storingmeans the part that has been unaffected by heat of molten metal and thepart that has been affected by the heat of the molten metal, processingand collecting the send that is separated and stored in the respectivestoring means by transferring the sands through the same path atdifferent times, and collecting them in respective storing means, mixingat a predetermined ratio the two kinds of collected sand, and adjustingthe moisture content in the mixed sand to use it as molding sand.
 7. Themethod of claim 6 wherein during the transfer through the same path, thestep for processing and collecting the sand that has been affected bythe heat of the molten metal differs from that for the sand that hasbeen unaffected by to heat of the molten metal.
 8. The method of claim 7wherein the step for processing and collecting the sand by transferringthe sands through the same path includes the step for adding moisture tothe sand according to the temperature of the collected sand and themoisture content.
 9. The method of claim 6 wherein after the step isperformed for adding the hinder to the sand that has been affected bythe heat of the molten metal and for adjusting the moisture content inthe sand, the sand that has been unaffected by the heat and that isstored is mixed with that sand at a predetermined ratio.
 10. The methodof claim 7 wherein after the step is performed for adding the binder tothe sand that has been affected by the heat of the molten metal and foradjusting the moisture content in the sand, the sand that has beenunaffected by the heat and that is stored is mixed with that sand at apredetermined ratio.
 11. The method of claim 8 wherein after the step isperformed for adding the binder to the sand that has been affected bythe heat of the molten metal and for adjusting the moisture content inthe sand, the sand that has been unaffected by the heat and that isstored is mixed with that sand at a predetermined ratio.
 12. The methodof claim 9 wherein after the step is performed for separately collectingin the storing means the part that has been unaffected by heat of moltenmetal and the part that has been affected by the heat of the moltenmetal, the two kinds of collected sand are mixed at a predeterminedratio, and then the binder is added to the mixed sand.
 13. The method ofclaim 10 wherein, after the step is performed for separately collectingin the storing means the part that has been unaffected by heat of moltenmetal and the part that has been affected by the heat of the moltenmetal, the two kinds of collected sand are inked at a predeterminedratio, and then the binder is added to the mixed sand.
 14. The method ofclaim 11 wherein, after the step is performed for separately collectingin the storing means the part that has been unaffected by heat of moltenmetal and the part that has been affected by the heat of the moltenmetal, the two kinds of collected sand are mixed at a predeterminedratio, and then the binder is added to the mixed sand.
 15. The method ofclaim 12 wherein the step for separating the main mold of green sand,after casting is conducted, into a part that has been unaffected by heatof molten metal and a part that has been affected by the heat of themolten metal is achieved by making the pressure negative in an airtightmember in which the green sand mold is put just after casting.
 16. Themethod of claim 13 wherein the step for separating the main mold ofgreen sand, after casting is conducted, into a part that has beenunaffected by heat of molten metal and a part that has been affected bythe heat of the molten metal is achieved by making the pressure negativein an airtight member in which the green sand mold is put just aftercasting.
 17. The method of claim 14 wherein the step for separating themain mold of green sand, after casting is conducted, into a part thathas been unaffected by beat of molten metal and a part that has beenaffected by the beat of the molten metal is achieved by making thepressure negative in an airtight member in which the green sand mold isput just after casting.
 18. The method of claim 6 wherein, after thestep is performed for separately collecting in the storing means thepart that has been unaffected by heat of molten metal and the part thathas been affected by the heat of the molten metal the two kinds ofcollected sand are mixed at a predetermined ratio, and then the binderis added to the mixed sand.
 19. The method of claim 7 wherein, after thestep is performed for separately collecting in the storing means thepart that has been unaffected by heat of molten metal and the part thathas been affected by the heat of the molten metal, the two kinds ofcollected sand are mixed at a predetermined ratio, and then the binderis added to the mixed sand.
 20. The method of claim 8 wherein, after thestep is performed for separately collecting in the storing means thepart that has been unaffected by heat of molten metal and the part thathas been affected by the heat of the molten metal, the two kinds ofcollected sand are mixed at a predetermined ratio, and then the binderis added to the mixed sand.
 21. The method of claim 18 wherein the stepfor separating the main mold of green sand, after casting is conducted,into a part that has been unaffected by heat of molten metal and a partthat has been affected by the heat of the molten metal is achieved bymaking the pressure negative in an airtight member in which the greensand mold is put just after casting.
 22. The method of claim 19 whereinthe step for separating the main, mold of green sand, after casting isconducted, into a part that has been unaffected by heat of molten metaland a part that has been affected by the heat of the molten metal isachieved by making the pressure negative in an airtight member in whichthe green sand mold is put just after casting.
 23. The method of claim20 wherein the step for separating the main mold of green sand, aftercasting is conducted, into a part that has been unaffected by heat ofmolten metal and a part that has been affected by the heat of the moltenmetal is achieved by making the pressure negative in an airtight memberin which the green sand mold is put just after casting.
 24. The methodof claim 6 wherein the step for separating the main mold of green sand,after casting is conducted, into a part that has been unaffected by heatof molten metal and a part that has been affected by the heat of themolten metal is achieved by making the pressure negative in an airtightmember in which the green sand mold is put just after casting.
 25. Themethod of claim 7 wherein the step for separating the main mold of greensand, after casting is conducted, into a part that has been unaffectedby heat of molten metal and a part that has been affected by the heat ofthe molten metal is achieved by making the pressure negative in anairtight member in which the green sand mold is put just after casting.26. The method of claim 8 wherein the step for separating the main moldof green sand, after casting is conducted, into a part that has beenunaffected by heat of molten metal and a part that has been affected bythe heat of the molten metal is achieved by making the pressure negativein an airtight member in which the green sand mold is put just aftercasting.
 27. An apparatus for processing collected sand that isseparated and collected from a main mold of green sand after castingcomprising means for separating each main mold of green sand into a partthat has been unaffected by heat of molten metal and a part that hasbeen affected by the heat of the molten metal and storing the parts,means for separately collecting the part that has been unaffected byheat of molten metal and the part that has been affected by the heat ofthe molten metal, which parts are separated and stored, means forseparately storing the part that has been unaffected by the heat of themolten metal and the part that has been affected by that heat, whichparts are separately collected, clay- and moisture-content-adjustingmeans for adding a binder to the part that has been affected by the heatand adjusting the moisture content in the part, blending means forblending the part that has been unaffected by the heat of the moltenmetal and the part that has been affected by that heat at apredetermined ratio, and mixing means for adjusting the moisture contentin the parts and mixing the parts.